Well, here goes. There's a set of plans for the Philadelphia in Chapelle's History of the American Sailing Navy. She was a handsome ship, she has some historical importance (albeit briefly), and I've never seen a model of her.
Unfortunately there were some pretty big differences between her and the Constitution. The Constitution is considerably bigger, and the hull lines are quite a bit different. In addition to the differences in the transom, the Philadelphia had a different figurehead; that in itself would be quite a project. I think the Philadelphia would be a great model subject, but an accurate model of her would really have to be scratchbuilt.
In the past few years quite a few people have dug into the history of the Constitution's appearance. It has indeed changed a great deal. I have more respect for the big Revell kit than some people do. Some details of it have been shown to be a little questionable on the basis of recent research, but it's based on the plans George Campbell did for the Smithsonian and in my opinion he did a good job. (This subject has been taken up in some detail elsewhere in this forum.)
I recommend two fairly recent books: A Most Fortunate Ship, by Tyron G. Martin, and Old Ironsides, by Thomas Gilmer, with watercolors by William Gilkerson. Martin was the Constitution's commanding officer at the time of the Bicentennial, when the Navy poured some money into restoring her. Gilmer is an instructor of naval architecture at the Naval Academy, and was involved in her most recent restoration, just a few years ago - the project that led to her sailing under her own power again. Gilkerson is a superb marine artist who takes great pains with his research. Both books contain reproductions of old paintings and of newly-commissioned ones, in an effort to establish her appearance at various crucial moments. I don't have either in front of me at the moment, but as I recall there's a painting in one of them by Tom Freeman depicting the assault on Tripoli. That would be a good start.
To modify the Revell kit into "Barbary Wars configuration" would be a major project, but do-able. The bulwarks would have to be changed, several major details of the rig would need revision - and she'd need a new figurehead (Hercules carrying a club in one hand and the Constitution in the other). If I remember correctly, she didn't have a stripe through her gunports at that time; the sides of the hull were natural, oiled oak, and the wales and rails were "blackened."
Two recent wood Constitution kits, by Bluejacket and Model Shipways, make great claims to historical accuracy. I haven't examined either of them, but I believe the instruction manuals (which, I think, are sold separately) contain quite a bit of information about her changing configurations. Both were developed with the help of the U.S.S. Constitution Museum - which, by the way, probably would be a good source as well. I suspect the folks there have lots of documents at their disposal and can answer questions with about as much authority as anybody.
To get an idea of what you're up against, take a look at Donald McNarry's Ship Models in Miniature. McNarry gets my vote for the title Best Ship Modeler in the World. Among his hundreds of small-scale models he's done several Constitutions on the scale of 1/16"=1', and they're incredible. One is in the Naval Academy Museum; another was on loan from the Smithsonian to the Mariners' Museum at Newport News the last time I heard. I arranged the loan when I worked at the Mariners' Museum, because I'd admired the model so much when I'd visited the Smithsonian. It represents the ship as built (much as she looked during the Barbary Wars). When the model arrived at the museum I sent some photographs of it to Captain Martin and asked for his comments on it. He agreed that it was an outstanding example of model building, but found about a dozen mistakes in terms of accuracy.
That's the best I can do off the top of my head. My advice is to start with the Martin and Gilmer books, and, if possible, make a trip to Boston. While you're in that neighborhood, you'll want to swing by the Peabody-Essex Museum in Salem and take a look at the "Isaac Hull model." If you get a look at either of the McNarry models in the flesh, be warned: they may make you give up on model building altogether.